Quenching device and quenching method

ABSTRACT

A quenching device is described that includes at least one chamber that can be filled with quenching gas and that has a blower wheel for circulating quenching gas, in particular a quenching chamber and/or a flow channel, a drive motor, situated outside the chamber, for driving the blower being allocated to the blower wheel. The drive motor is coupled to the blower wheel so as to transmit torque via a coupling that operates in contactless fashion. Also described is a related quenching method.

FIELD OF THE INVENTION

The present invention relates to a quenching device for quenchingmaterial that is to be quenched, in particular metallic workpieces,using quenching gas, as well as a quenching method for quenchingmaterial that is to be quenched, in particular metallic workpieces,using quenching gas.

BACKGROUND INFORMATION

In order to produce defined material properties, such as a high degreeof hardness or sufficient resistance to wear, workpieces, usually madeof metal, are subjected to thermal treatment. The most important factorin determining the result of this treatment is the speed with which theworkpieces are cooled after having been heated. It is known to usewater, oil, or quenching gas for the quenching process necessary forthis purpose. The main advantage of using quenching gases instead ofquenching liquids is that the material being quenched does not have tobe cleaned after quenching, and that a higher degree of quenchinghomogeneity can be achieved in the batch.

A quenching device used for a quenching process as discussed above isdiscussed for example in EP 1 154 024 B1. The foregoing device has achamber that can be flooded with quenching gas, formed by a quenchingchamber for accommodating the material that is to be quenched and by aflow channel for the formation of a quenching gas flow circuit. Thequenching chamber is loaded and unloaded not while flooded withquenching gas, but rather, as a rule, under vacuum. In the knownquenching device, in order to form a quenching gas flow a blower wheelis situated in the flow channel that is driven by an electric motor thatis situated outside the chamber that can be flooded with quenching gas.Because a motor shaft of the drive motor passes through an outer wall ofthe flow channel, a large constructive outlay is necessary in order toachieve a hermetic seal of the chamber that can be flooded withquenching gas.

In alternative known quenching devices, the drive motor is situated,together with the blower wheel, inside the chamber that can be floodedwith quenching gas, in order to avoid leakages. Here there is theproblem that the drive motor cannot be started in a vacuum, becauseotherwise electrical flashovers (arcs) could arise in the winding of thedrive motor that could destroy the drive motor. This is problematic tothe extent that the powerful blowers required in order to increase thequenching rate require long start-up times, relative to the actualquenching duration, to reach their nominal rotational speed. Because thedrive motor cannot be started during the loading of the quenchingchamber under a vacuum atmosphere, but rather has to take place afterthis chamber has been flooded with quenching gas, the overall start-uptime is added to the actual quenching duration, which has a negativeeffect on the cycle rate that is to be achieved.

The described disadvantage results overall in a slower quenching of thematerial compared to quenching using liquids, because with the use ofliquids the maximum quenching intensity is available immediately afterthe immersion of a batch that is to be quenched in the liquid bath. Inquenching devices having drive motors situated inside the chamber thatis to be flooded, the reduced quenching speed affects not only the cycletime, but also, due to the prolonged quenching duration, the quality ofthe workpiece joining, and thus also the properties of the components.

SUMMARY OF THE INVENTION

The exemplary embodiments and/or exemplary methods of the presentinvention are based on an object of providing a quenching device inwhich leakage problems are avoided and in which a starting of thepowerful drive motor for the blower is possible even before the floodingof the chamber with quenching gas, in particular when there is a vacuumin the chamber. In addition, an object of the exemplary embodimentsand/or exemplary methods of the present invention is to indicate amethod that enables operation of the blower drive motor independent ofthe atmosphere in the chamber in which the blower wheel is situated.

With regard to the quenching device, this object is achieved by thefeatures described herein, and with regard to the method the object isachieved by the features also described herein. Advantageousdevelopments of the exemplary embodiments and/or exemplary methods ofthe present invention are indicated further herein. The scope of theexemplary embodiments and/or exemplary methods of the present inventioninclude all combinations of at least two features disclosed in theentire disclosure of the present application, including the descriptionand/or the Figures.

The exemplary embodiments and/or exemplary methods of the presentinvention recognize that operation of the drive motor (which may befashioned as a standard electric motor) for the at least one blowerwheel independent of the atmosphere and pressure conditions in thechamber accommodating the blower wheel is possible only if the drivemotor is situated outside this chamber. Because in the prior art themotor shaft of the drive motor passes through the wall of the chamber,problems with leakage are necessarily present in the prior art. In orderto avoid this problem, the exemplary embodiments and/or exemplarymethods of the present invention provides that the drive motor becoupled to the blower wheel not mechanically, as in the prior art, butrather in contactless fashion. In other words, the drive motor and theblower wheel are provided with a coupling that is fashioned such thatthis coupling is capable of transmitting, without contact, a torque fromthe drive motor to the blower wheel. In this way, it is not necessaryfor mechanical components of the drive train to pass through the wall ofthe chamber, thus avoiding leakage problems.

The situation of the drive motor outside the chamber that can be floodedwith quenching gas and in which a vacuum may be produced additionallymakes it possible to start up the powerful drive motor before thechamber is flooded with quenching gas, which may be early enough thatthe drive motor has already reached its nominal rotational speed at thebeginning of the actual quenching process, i.e., as a rule, when thechamber is completely flooded with quenching gas. A further advantage ofthe quenching device designed in this way is that it is not necessary touse specially sealed motors; rather, comparatively inexpensive standardelectric motors may be used. A specific embodiment of the quenchingdevice quite particularly may be used in which the coupling by which adrive torque can be transmitted from the drive motor to the blower wheelis fashioned as a magnetic coupling capable of transmitting torquethrough the wall of the chamber.

A specific embodiment may be particularly provided in which the magneticcoupling has a first rotor connected mechanically to the drive motor,which may be to a motor shaft of the drive motor, and has a second rotordrivable in contactless fashion by the first rotor and connectedmechanically to the blower wheel, the second rotor together with theblower wheel being situated in the chamber that can be flooded withquenching gas.

According to a first alternative, the rotor coupled mechanically to thedrive motor is an inner rotor surrounded radially outwardly by thesecond rotor driven in contactless fashion, the inner rotor being setinto rotational movement by the rotationally moved magnetic field.

The converse variant may also be realized. Here, the second rotor, i.e.the rotor driven in contactless fashion, is an inner rotor surroundedradially outwardly by the first rotor (outer rotor). The latter specificembodiment is a particular variant.

In a development of the exemplary embodiments and/or exemplary methodsof the present invention, it is advantageously provided that the blowerwheel is situated immediately in the quenching chamber, i.e. in thechamber that is immediately to be loaded with material to be quenched.In an alternative specific embodiment, the blower is situated in a flowchannel that is connected in terms of flow to the quenching chamber. Theprovision of a flow channel is optional; i.e., a specific embodiment ofthe quenching device as a quenching cell not having a flow channel mayalso be realized; i.e., a specific embodiment in which the quenching gasis circulated exclusively in the quenching cell by the blower.

A specific embodiment of the quenching device may particularly be usedin which this device has a flooding arrangement for flooding the chamberhaving the blower wheel with quenching gas. Particularly, the floodingarrangement may include a gas supply line that opens into the chamber,the supply line being fed by a pressure tank filled with quenching gas.

It may be further provided that an evacuating arrangement may beprovided for evacuating the quenching device. These evacuatingarrangement may be configured such that low pressure compared to thesurrounding environment can be produced in the quenching chamber; i.e.,a vacuum can be produced in the chamber.

Quite particularly, a heat exchanger may be situated in the chamberhaving the blower wheel, said heat exchanger being charged with thequenching gas circulated by the blower wheel and removing heat from thisgas in a targeted manner.

The present invention is also directed to a method for quenchingmaterial to be quenched, in particular metallic workpieces, withquenching gas using a quenching device, which may be a quenching deviceas described above. In the method, the blower wheel is used toaccelerate the quenching gas in order to realize a good heattransmission between the material being quenched and the quenching gas.The core of the method of the present invention is that the blower wheelis driven by the drive motor in contactless fashion, in particular usinga magnetic coupling. This specific embodiment makes it possible totransmit the torque through a wall and thus to situate the drive motoroutside the chamber in which the blower wheel is situated.

It may be quite particularly provided that the drive motor is alreadystarted and/or operated while the chamber is not (yet) flooded withquenching gas. Given the use of a standard drive motor that is notsealed, this is possible only if the drive motor is not situated in theflooded chamber.

Further advantages, features, and details of the present inventionresult from the following description of the exemplary embodiments, andon the basis of the drawing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic representation of a possible design of aquenching device.

DETAILED DESCRIPTION

FIG. 1 shows a possible specific embodiment of a quenching device 1. Inthe depicted exemplary embodiment, quenching device 1 has a singlechamber 2 that can be flooded with quenching gas. A floodable chamber inthe form of a flow channel as shown in EP 1154 024 B1 does not existhere, but can be provided if needed.

Chamber 2 has a loading door 3 that can be sealed in pressure-tightfashion, through which chamber 2 (here the quenching chamber) can beloaded with material 4 that is to be quenched. For this purpose,material 4 that is to be quenched, which in the depicted exemplaryembodiment is made up of steel workpieces, is placed on a charging rack5 that, using suitable transport devices, can be transported intochamber 2 under a vacuum atmosphere and then transported out of saidchamber after the quenching process.

An oven (not shown) for the preliminary heat treatment of quenchingmaterial 4 is standardly situated in front of loading door 3.

A quenching gas supply line 6 opens into chamber 2, via which quenchinggas can be conducted into chamber 2 from a pressure gas container 7. Inorder to flood chamber 2 with the quenching gas, it is necessary merelyto open a valve 8, which may be automatically.

The pressure in chamber 2 after the flooding with quenching gas may beup to approximately 20 bar.

Inside chamber 2, a blower wheel 9 (fan wheel) is mounted so as to becapable of rotation, blower wheel 9 being situated on the end of a shaft10 that on its opposite end bears a second rotor 11 (here an innerrotor) of a magnetic coupling 12. Shaft 10 extends with second rotor 11into a protuberance 13 of chamber 2 that is surrounded radiallyoutwardly by a first rotor 14 (here an outer rotor) of magnetic coupling12. First rotor 14 is situated at a (radial) distance from second rotor11, and, when drive motor 15 is running, transmits a torque incontactless fashion through wall 16 of chamber 2, or, more precisely,through wall 16 of protuberance 13 of chamber 2, to second rotor 11,which consequently rotates along with the first rotor, setting blowerwheel 9 into rotational movement. First rotor 14 is seated inrotationally fixed fashion on the end of a motor shaft 17 of drive motor15, which is fashioned as a standard electric motor. It is essentialthat drive motor 15 be situated outside wall 16 of chamber 2, i.e. whichmay be in a normal air atmosphere, so that drive motor 15 can beoperated independent of the atmosphere and internal pressure in thechamber.

FIG. 1 also shows that a heat exchanger 18 is situated inside chamber 2that withdraws heat from quenching gas not circulated by blower wheel 9.

In the following, a particular quenching process is described in detail.First, loading door 3 is opened and charging rack 5, with material 4that is to be quenched, is introduced into chamber 2, in which there maybe a vacuum. The drive motor 15 may be started already during thisloading. After loading door 3 is closed, chamber 2 is flooded withquenching gas via quenching gas supply line 6 until the quenchingpressure is reached. Drive motor 15 and, as a consequence, blower wheel9 have already reached their nominal rotational speed by the end of theflooding process, so that immediately after the termination of theflooding process the full quenching intensity is available. After apredetermined quenching time, the quenching gas is either released tothe surrounding environment or is conveyed back into pressure gascontainer 7 via a compressor (not shown), and loading door 3 is removedin order to remove charging rack 5 with the quenched material 4. Avacuum may then be produced in chamber 2.

1-10. (canceled)
 11. A quenching device, comprising: at least onechamber, which is fillable with a quenching gas and which has a blowerwheel for circulating the quenching gas, wherein the at least onechamber includes at least one of a quenching chamber and a flow channel;and a drive motor, which is situated outside the chamber, for drivingthe blower being allocated to the blower wheel; wherein the drive motoris coupled to the blower wheel so as to transmit torque via a couplingthat operates in contactless fashion.
 12. The quenching device of claim11, wherein the coupling includes a magnetic coupling.
 13. The quenchingdevice of claim 12, wherein the magnetic coupling includes a first rotorconnected mechanically to the drive motor and a second rotor, which isdrivable in contactless fashion by the first rotor and which ismechanically connected to the blower wheel.
 14. The quenching device ofclaim 13, wherein the first rotor includes an outer rotor, radiallyoutwardly surrounding the second rotor, which is fashioned as an innerrotor.
 15. The quenching device of claim 13, wherein the second rotorincludes an outer rotor, radially outwardly surrounding the first rotor,which includes an inner rotor.
 16. The quenching device of claim 11,wherein material to be quenched is situatable in the chamber having theblower wheel.
 17. The quenching device of claim 11, further comprising:a flodding arrangement to flood the chamber with quenching gas.
 18. Thequenching device of claim 11, wherein a heat exchanger is situated inthe chamber.
 19. A method for quenching material to be quenched withquenching gas, the method comprising: circulating quenching gas, using aquenching device, with a blower wheel driven by a drive motor, whereinthe blower wheel is driven by the drive motor in contactless fashion;wherein the quenching device, includes at least one chamber, which isfillable with the quenching gas and which includes the blower wheel forcirculating the quenching gas, wherein the at least one chamber includesat least one of a quenching chamber and a flow channel, and the drivemotor, which is situated outside the chamber, for driving the blowerbeing allocated to the blower wheel.
 20. The method of claim 19, whereinthe drive motor is at least one of started up and operated while thechamber is not yet flooded with quenching gas.
 21. The method of claim19, wherein the quenching material includes a metallic workpiece.